Elevator systems are useful for carrying passengers between various levels in a building. There are various types of elevator systems. Some are referred to as traction-based systems because of reliance upon traction between a drive sheave and hoisting ropes to move and position the elevator car. Elevator machines in traction-based systems include a motor, drive sheave and a brake. There are a variety of known brake configurations.
Some elevator codes require braking functions that are not provided by older machines. Supplemental brakes can be added to meet such code requirements. One type of supplemental brake is referred to as a rope grabber because it provides a mechanism for clamping onto the roping arrangement. A rope grabber prevents the roping arrangement from moving, which maintains a position of an elevator car within a hoistway.
Rope grabber braking has drawbacks. One drawback is that the rope grabber system needs to be positioned below the elevator machine. This requires taking up space within the hoistway or raising the elevator machine within a machine room for providing adequate spacing for the rope grabber system. Raising elevator machines is very costly, requires adequate clearance in the machine room, and may require new ropes. Such installation is cramped, resulting in limited accessibility for future service. Additionally, some elevator applications exceed the capability of existing available rope grabbing devices, or have other space limitations. Rope grabbers, by applying braking forces directly onto the ropes, increase rope wear.
Other options to meet contemporary regulatory braking requirements include replacing the existing elevator machine with a completely new machine that includes necessary braking capabilities. Such action, however, can be costly and time consuming, and results in wasting otherwise serviceable elevator machinery.
The rotating portion of an elevator machine includes a main shaft assembly supported on bearings. The main shaft bearings are supported in stands or housings on the stationary structure of the machine. The main shaft bearings are arranged to support large radial loads developed by the weight of the motor shaft assembly, the weight of the elevator car 22 (FIGS. 1 and 2) and other loads transmitted to the elevator drive sheave by the roping arrangement 26.
The main shaft bearings may be implemented as sleeve bearings, also known as journal bearings. The main shaft bearings may alternatively be implemented as rolling element bearings, also known as anti-friction bearings.
On some elevator machines, the main shaft bearings allow some amount of axial movement of the main shaft during rotation and operation of the elevator machine. Axial movement of the main shaft may occur in main shaft designs utilizing sleeve bearings and also designs utilizing rolling bearing elements.
When applying certain componentry to the main shaft, for proper operation of the componentry the axial movement of the main shaft must be held at or near to zero. Disc brake componentry, e.g., tolerates zero or near zero axial movement of the main shaft for proper operation.
Innovations have sought to enhance braking of installed elevators by replacing contemporary braking componentry with disc brake componentry. In view of tight tolerances associated with disc brakes, the pending disclosure provides a system that limits axial motion for the main shaft disposed between shaft bearing stands.